1. Field of the Invention
A process and apparatus for controlling the delivery of drawing ink to an automatic drawing or drafting machine, and particularly a machine having a plurality of selectively controlled tubular writing pens, for drafting different line widths.
2. Description of the Prior Art
In an earlier procedure of this type, (German P No. 27 41 311) (U.S. Ser. No. 907,536, now U.S. Pat. No. 4,188,634), the ink level in an intermediate chamber was controlled by comparing an actual value with a theoretical value. The intermediate chamber was connected with both the ink delivery mechanism and the stylographic, or tube, pens in such a manner that a static ink pressure resulted in the writing tubes of the attached tube pens, which pressure was determined by the ink level of the intermediate chamber.
Even though this earlier procedure functioned satisfactorily, it required nontheless a relatively complex switching process to compare the actual value with the theoretical value and to correspondingly activate the ink delivery mechanism. Beyond that, it established the same static ink pressure for all tube pens. It is, however, also known that the static ink pressure must be adjusted to correspond to the line width of the tube pen in order to achieve optimal results, i.e., the narrow width tube pen should have a greater static pressure at its tube writer than a wide width tube pen.
The object of the invention is, therefore, to provide a simple means of individually adapting the static ink pressure in a number of tube pens to the line width of each tube pen.
The solution to this object is provided by maintaining a constant static pressure for each pen, as a function of its line width. The preferred embodiments of the invention employ a process by which the ink delivery mechanism provides ink to the tube pen with the smallest line width, which ink in turn flows through an overflow located at a predetermined height, and successively to tube pens with overflows at lower levels, and progressively greater line widths, and finally, as necessary, through a supply chamber back to the ink delivery mechanism. The ink delivery system functions preferably continuously.